Sound recorder and reproducer



Feb. 1, 1938. M. BENDER 2,107,050

SOUND RECORDER AND REPRODUCER Filed July 8, 1953 Qflj wu 4, 1/4 lllllllHlll l I I I [I I INVENTOR ATTORNEY Patented Feb. 1, 1938 UNITED STATESSOUND RECORDER AND REPRODUCER,

Max Bender, Astoria, N. Y., assignor, by mesne assignments, to UnitedAcoustigraph Corporation, a corporation of Nevada Application July 8,1933, Serial No. 679,465

1 Claim.

This invention relates to a recording and reproducing of sound, and hasfor its object an improved apparatus for recording sound in the form ofa groove in relatively hard material, such for 5 example, as celluloidor motion picture film. A further object is toprovide an improved devicewhich may be used alternately as a sound recorder and reproducer. Afurther object is to provide an improved form of cutting stylus.

Other objects and advantages of my invention will appear from thefollowing description taken in connection with accompanying drawing,wherein;

Figure 1 is a top plan view of a sound recorder and reproducer embodyingone form of my invention;

Figure 2 is a sectional view partly in elevation taken on the line 2--2of Figure 1 and also 22 of Figure3, and showing in addition an anvilwith a strip of film thereon;

Figure 3 is a sectional view taken on the line 3--3 of Figure 2; v

Figure 4 is a sectional view taken on the line 4-4 of Figure 2;

Figure 5 is an enlarged detail view showing the relative position of themovable, stylus operating, armature and the pole pieces between whichthe armature vibrates;

Figure 6 is a greatly enlarged side elevation of an improved form of acutting stylus;

Figure 7 is a bottom plan view of the structure shown in Figure 6;

Figure 8 is a sectional view taken on the line 8-8 of Figure 6;

Figure 9 is a circuit diagram of the electrical connections through thearmature operating coils; and

Fig. 10 is a plan view of an armature and stylus holder showing amodification.

Referring more particularly to Figures 2 to 4 inclusive, referencecharacter l represents a permanent horse-shoe magnet which is adapted tobe supported by a plate ll of brass or other non-magnetic materialbolted or screwed at l2 to the ends of the poles of the magnet [0. PlateII is provided with elongated openings 3 by which the recorder may beadjustably secured in suitable support.

Secured to the sides of the permanent magnet H! by cement or any othersuitable manner and extending inwardly therefrom are four coils, l4, l5,l6 and I1 respectively, arranged as shown in Figure 4. Each of the coilshas an adjustable core l8, preferably of soft iron, forming at theirinner ends two pairs of opposing pole pieces. The

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opposite end of each core is extended and screw threaded, and is adaptedto be received in screw threaded opening 22 in the side of the permanentmagnet l0, thus providing for the adjustment of the core.

Positioned between the pole pieces of each pair and adapted to vibrateon a vertical axis is an armature 25 of soft (Norway) iron. Armature 25is supported by adjustable pivot bearings 21 and 28, securedrespectively in the plate II and 10 in a brass plate 29 attached atopposite ends to the sides of the permanent magnet II], the armaturepreferably being provided pivot cups of hardened steel.

Plate II at opposite sides of the bearing 21 is 15 formed with openings30 and 3| through which extend downwardly projecting parts 32 and 33 ofthe armature 25. The part or extension 32 of the armature carries at itslower end a recording stylus 34 and extension 33 of the armature may, 20if desired, carry at its lower end reproducing stylus 35.

Mounted at one side of the permanent magnet l0 and extending inwardlytherefrom at opposite sides of the pivotal axis of the armature are ad-85 justable cushioning means, consisting of nonmagnetic screw threadedrods 40 received in screw threaded openings 4|, and adjustably held inplace by lock nuts 42. The inner ends of the rods 40 are formed as cups45 which contain rub- 80 her or other cushioning material 45a whichextends outside of the cup and is constantly in contact with the side ofthe armature 25. It is to be noted that the armature in horizontal crosssection is slightly tapered outwardly from its axis. 35 By forming thearmature in this way, I find that I obtain more satisfactory contact ofthe armature with the pads and a more satisfactory operativerelationship of the armature to the pole pieces, and at the same timeprovide sufiicient material at the center of the armature for itsadequate support on the pivot bearings.

In Figure 2 I show an anvil 50 over which extends a strip of film 5|,which is adapted to be moved in the direction of the arrow 52 during therecording operation. After a record is made, it may be reproduced byadjusting the plate ll so that the reproducing stylus 34 rests in thegroove of the film. Occasionally it is desired to record a groove on afilm by moving the film in one direction, and then continue therecording by moving the film in the opposite direction. When this isdone, I mount a recording stylus at the ends of both extensions of thearmature as shown, for example, in Fig. 10, the stylu l6 carried by oneextension 32 being adapted to record while the film is moved in thedirection of the arrow 52 of Fig. 2 and the stylus carried at the end ofthe other extension being adapted to record when the film is moved inthe opposite direction. 7

It will be noted from Figure 9 that the coils l4 to l1 are so wound asto tend to make oppo-. site poles of each pair of opposite sign, a northpole being opposite to a south pole and also corresponding poles of thetwo pair are of opposite faces 61, leaving between them a portion 68 ofthe original tapered surface 64. Theeflect ofgrinding or under-cuttingto form surfaces 61 is to sharpen the curved edge 69 at opposite sidesof the axis of the stylus where the upper surface 66 meets the lowersurface of the stylus.

As the tapered surface 64 is conicalit is a comparatively simpleoperation to grind away this surface to a proper depth. The angle abetween the upper surface 66 and the portion 68 of the tapered surface64 should be between 25 and maximum. The angle b; as shown in Figure 8,between the surface 61 and the upper surface 66, should be between 20and 30 maximum. I find that by forming the stylus in this manner, withthe angles above given, I not only secure satisfactory cutting but thereis sufiicient material back of the cutting edge to properly strengthenthe stylus and minimize the breakage. In making a sound groove of thelateral type, the angle between the surface 68 and the tangent to thefilm at the cutting point should be approximately 25. 7

It will, of course, be understood that during the recording operationcurrent which varies in The variation may be generated by a suitablemonophone actuated by thesource of sound and the monophone currentamplified by thermionic valves. ,In reproducing, the coils l4 to I! willbe energized from a source of constant potential and the variations ofcurrent produced by vibrations of the armature 25. suitably amplifiedandreproduced as sound. The stylus as described makes a clean cut in thefilm, removing from the film a finethread of the film materiaL' Havingnow described my invention, what I claimand desire to secure by LettersPatent is:

In a device of the character described, a magnet having opposite poles,a fiat U shaped member of magnetic material pivotally supported atapproximately the center of the bend of the U, and the, bend of the Ubeing located between and under the influence of said poles, and astylus secured directly in the end of each leg of the U.

- MAX BENDER.

